--------------------
- Experimental evidence of a mechanical coupling between layers in DWNTs

Auteur(s): Michel T.

Conférence invité: Third International Workshop on Nanocarbon Photonics and Optoelectronics (Polvijärv, FI, 2012-07-29)


Résumé:

The combination of transmission electron microscopy, electron diffraction and resonant Raman spectroscopy on individual suspended nanostructures is the ultimate method to relate unambiguously theirs structural parameters [1], optical transitions [2, 3], and Raman-active phonons [1, 3, 4]. This approach has been successfully used to study the main Raman-active modes of individual double-walled carbon nanotubes [5] (DWCNT). In this contribution, we will show, in particular, that low-frequency features in the Raman spectra cannot be connected to the layer diameters d by means of the 1/d power law, widely used for the diameter dependence of the radial-breathing mode of single-walled nanotubes. We discuss this disagreement in terms of mechanical coupling between the layers of the DWCNT, which results in collective vibrational modes. The mechanical coupling qualitatively explains the observation of Raman lines of breathing-like modes, whenever only one of the layers is in resonance with the laser energy. [1] J. C. Meyer, M. Paillet, M. ; Michel, T. ; Moréac, A. ; Neumann, A. ; Duesberg, G. S. ; Roth, S.; Sauvajol, J.-L., Phys. Rev. Lett., 95, 217401 (2005). [2] T. Michel, M. Paillet, J.C. Meyer, V.N. Popov, L. Henrard, J.L. Sauvajol, Phys. Rev. B, 75, 155432 (2007). [3] M. Paillet, T. Michel, J.C. Meyer, V.N. Popov, L. Henrard, S. Roth, J.L. Sauvajol, Phys. Rev. Lett., 96, 257401 (2006). [4] T. Michel, M. Paillet, D. Nakabayashi, M. Picher, V. Jourdain, J.C. Meyer, A.A. Zahab, J.L. Sauvajol, Phys. Rev. B, 80, 245416 (2009). [5] D. Levshov, T. X. Than, R. Arenal, V. N. Popov, R. Parret, M. Paillet, V. Jourdain, A. A. Zahab, T. Michel, Yu. I. Yuzyuk, and J.-L. Sauvajol, Nano Lett., 11, pp 4800–4804 (2011).